Abstract. Formation of new aerosol particles by nucleation and growth is a significant
source of aerosols in the atmosphere. New particle formation events usually
take place during daytime, but in some locations they have been observed
also at night. In the present study we have combined chamber experiments,
quantum chemical calculations and aerosol dynamics models to study nocturnal
new particle formation. All our approaches demonstrate, in a consistent
manner, that the oxidation products of monoterpenes play an important role
in nocturnal nucleation events. By varying the conditions in our chamber
experiments, we were able to reproduce the very different types of nocturnal
events observed earlier in the atmosphere. The exact strength, duration and
shape of the events appears to be sensitive to the type and concentration of
reacting monoterpenes, as well as the extent to which the monoterpenes are
exposed to ozone and potentially other atmospheric oxidants.